Cross-conduction in switching regulators occurs when a high-side switch (connected to the input of a power supply) and low-side switch (connected to ground) are turned on at the same time, thereby creating a short circuit from the input supply to ground. This can lead to large current spikes and voltage transients that can degrade the reliability of the switches and decrease performance of precision circuits. Cross-conduction can be avoided by ensuring that the signal that turns on the high-side switch (HDRV) is not high at the same time as the signal that turns on the low-side switch (LDRV). In other words, a non-overlap or “dead-time” between the HDRV and LDRV signals should be provided by circuit design principles and tolerances. One issue with design tolerances is that to ensure there is no signal overlap, more dead-time may be selected than required, which can result in decreased efficiency of the switching regulator. Automated testing systems can be employed to measure the HDRV and LDRV signals to determine if any overlap exists while testing for a minimum of dead-time to promote efficiency.
There are two instances when cross-conduction can occur because of signal overlap. In one instance, overlap can occur when the LDRV signal is rising high (low-side switch is turning on) and HDRV is falling low (high-side switch is turning off). The other overlap case is when the HDRV signal is rising high and the LDRV is falling low. Unfortunately, for switching regulator integrated circuits (ICs) having integrated switches, the HDRV and LDRV signals are internal to the chip and thus not readily observable by test equipment to ensure that they do not overlap. An obvious solution is to route the drive signals external to the IC for testing but such strategy can increase costs of the IC by adding extra pins and also introduce noise in the system.